1. Field of the Invention
The present invention relates to a semiconductor device including a MISFET (Metal Insulator Semiconductor Field Effect Transistor) in which the gate insulator contains a metal oxide, and a method of manufacturing the same.
2. Description of the Related Art
The improvements in the operating speed and in the degree of integration of an LSI (Large Scale Integrated) circuit are being promoted by the miniaturization of the MOS (Metal Oxide Semiconductor) device conforming with the scaling law. In the scaling law, the sizes of each portion of the MOS device such as the thickness of the insulating film and the gate length are reduced in substantially the same ratio in the height direction and the horizontal direction. As a result, it is possible to maintain or improve the characteristics of the device.
In next generation MOS transistors, the equivalent silicon oxide film thickness (Equivalent Physical Oxide Thickness, hereinafter referred to as “EOT”), which is the thickness of the gate insulator converted into the thickness of the silicon oxide film on the basis of the dielectric constant, is required to be not larger than 2 nm. However, if a silicon oxide film is used as a gate insulator, the EOT value noted above fails to sufficiently suppress the current leakage and, thus, a problem is generated that the power consumption is increased.
Under the circumstances, it is being studied in recent years to use a material having a dielectric constant higher than that of silicon oxide, such as a metal oxide or a silicate of silicon dioxide and metal oxide, as the material of the gate insulator for next generation MOS transistors. If such a material having a high dielectric constant is used for forming a gate insulator, it is possible to increase the actual thickness of the gate insulator so as to sufficiently suppress the current leakage, and to achieve an EOT value not larger than 2 nm.